This invention relates generally to inflatable restraint systems and, more particularly, to arrangements and methods involving inflatable device formation of inflation gas.
It is well known to protect a vehicle occupant using a cushion or bag, e.g., an "airbag cushion," that is inflated or expanded with gas when the vehicle encounters sudden deceleration, such as in the event of a collision. In such systems, the airbag cushion is normally housed in an uninflated and folded condition to minimize space requirements. Upon actuation of the system. The cushion begins to be inflated in a matter of no more than a few milliseconds with gas produced or supplied by a device commonly referred to as an "inflator."
Many types of inflator devices have been disclosed in the art for the inflating of one or more inflatable restraint system airbag cushions. Prior art inflator devices include compressed stored gas inflators, pyrotechnic inflators and hybrid inflators. Unfortunately, each of these types of inflator devices has been subject to certain disadvantages such as greater than desired weight and space requirements, production of undesired or non-preferred combustion products in greater than desired amounts, and production or emission of gases at a greater than desired temperature, for example.
In view of these and other related or similar problems and shortcomings, a new type of inflator, called a "fluid fueled inflator," has been developed. Such inflators are the subject of commonly assigned Smith et al., U.S. Pat. No. 5,470,104, issued Nov. 28, 1995; Rink. U.S. Pat. No. 5,494,312, issued Feb. 27, 1996; and Rink et al., U.S. Pat. No. 5,531,473, issued Jul. 2, 1996, the disclosures of which are fully incorporated herein by reference.
Such inflator devices typically utilize a fuel material in the form of a fluid, e.g. in the form of a gas, liquid, finely divided solid, or one or more combinations thereof, in the formation of an inflation gas for an airbag. In one such inflator device, the fluid fuel material is burned to produce gas which contacts a quantity of stored pressurized gas to produce inflation gas for use in inflating a respective inflatable device.
While such an inflator can successfully overcome, at least in part, some of the problems commonly associated with the above-identified prior types of inflator devices, there is a continuing need and demand for further improvements in safety, simplicity, effectiveness, economy and reliability in the apparatus and techniques used for inflating an inflatable device such as an airbag cushion.
To that end, the above-identified Rink, U.S. Pat. No. 5,669,629 discloses a new type of inflator wherein a gas source material undergoes decomposition or dissociation to form products including at least one gaseous product used to inflate an inflatable device. As disclosed in Rink, U.S. Pat. No. 5,669,629, a pyrotechnic load-containing initiator device or heat source can be actuated to commence dissociation or decomposition of the gas source material.
Such an inflator can be helpful in one or more of the following respects: reduction or minimization of concerns regarding the handling of content materials; production of relatively low temperature, non-harmful inflation gases; reduction or minimization of size and space requirements and avoidance or minimization of the risks or dangers of the gas producing or forming materials undergoing degradation (thermal or otherwise) over time as the inflator awaits activation.
In view of possibly varying operating conditions and, in turn, possibly varying desired performance characteristics, there is a need and a desire to provide what has been termed an "adaptive" inflatable restraint system. With an adaptive inflatable restraint system, one or more parameters such as the quantity, supply, and rate of supply of inflation gas, for example, can be selectively and appropriately varied dependent on one or more selected operating conditions such as ambient temperature, occupant presence, seat belt usage and rate of deceleration of the motor vehicle, for example.
While such adaptive systems are desirable, they typically require the inclusion of additional components either in the system or as a part of the associated inflator device itself. Such inclusion of one or more additional components may undesirably increase the size, cost and/or weight of the inflator device or associated system. For example, various proposed or currently available dual stage inflator devices, particularly pyrotechnic-based forms thereof, appear based on the principal of packaging together two separate inflators. As a result, such inflator combinations commonly include two distinct pressure vessels, two sets of filter or inflation gas treatment components, one for the output of each of the pressure vessels, and two distinct diffusers, again one for the output of each of the pressure vessels. Thus, it has been difficult to provide an adaptive inflator which will satisfactorily meet the size, cost and weight limitations associated with modern vehicle design.
Stored or compressed gas-based adaptive inflation systems may overcome or at least minimize certain of such disadvantages. For example, such corresponding inflator devices may contain or utilize a single or "common" gas storage chamber for the provision of two or, possibly, more levels of performance or inflation pressures such as by selectively heating the stored gas to selected higher levels of pressure. Nevertheless, there is a need and demand for even more flexible inflation systems such as may capably provide an even wider array of selectable performance options.
"Rise rate," i.e., the rate at which the gas output from an inflator increases pressure as measured when such gas output is directed into a closed volume, is a common vehicular airbag inflator performance parameter used in the design, selection and evaluation of an inflator for particular airbag restraint system installations. For example, under certain circumstances such as in the event of a collision of relatively low severity or in connection with the protection of an out-of-position occupant or at least certain occupants of relatively smaller size including, for example, young children, it may be desirable for the corresponding inflatable restraint airbag cushion to deploy more gradually e.g., the rise rate for the associated inflator device is less steep, i.e., more gradual or gentler.
Further, while airbag cushions were initially commonly installed in vehicles to provide occupant protection primarily in the case of a frontal collision, modern vehicle design has placed increased reliance on inflatable airbag cushions to provide protection from other forms of collision including side impact collisions and vehicle rollovers. At least partially as a result thereof, side impact and other associated airbag assemblies have or are becoming more common in modern vehicles. For example, the possible desirable inclusion of an airbag cushion which upon inflation takes or assumes a tubular or other selected form and such as may form a covering, sometimes referred to as a "curtain" and such as may serve to cover a side, front or rear vehicle window, for example, has become increasingly apparent.
With the trend towards the inclusion of a greater number and variety of inflatable safety devices in modern vehicle design however, there is a desire and a growing apparent need for inflation system simplification such as may avoid the need for dedicated inflator devices for each such inflatable device and the costs associated with the design, manufacture, installation and maintenance of each such dedicated inflator device.
There remains a continuing need and demand for further improvements in safety simplicity, effectiveness, economy and reliability in the apparatus and techniques used for inflating inflatable restraints such as airbag cushions. More specifically, there is a need and a demand for improvements in inflatable restraint systems such as may provide or result in increased or greater flexibility of operation such as may better permit particular inflatable restraint systems to either or both:
1) be better tailored or adapted for use in specific or particular vehicle designs or
2) better provide or result in safe, simple, effective, economical, and/or reliable occupant protection to various vehicle occupants under an even greater variety of circumstances or conditions.
Further, there is a need and demand for inflatable restraint system design such as may more safely, simply, effectively, economically and/or reliably permit or allow inflation of multiple inflatable restraints such as airbag cushions as are more and more commonly being incorporated in modern vehicle design such as to provide increased or improve occupant protection.